title: Expression of microRNA and their gene targets are dysregulated in preinvasive breast cancer.
abstract: BACKGROUND
  microRNA (miRNA) are short, noncoding RNA that negatively regulate gene expression and may play a causal role in invasive breast cancer. Since many genetic aberrations of invasive disease are detectable in early stages, we hypothesized that miRNA expression dysregulation and the predicted changes in gene expression might also be found in early breast neoplasias.
  
  
  METHODS
  Expression profiling of 365 miRNA by real-time quantitative polymerase chain reaction assay was combined with laser capture microdissection to obtain an epithelium-specific miRNA expression signature of normal breast epithelium from reduction mammoplasty (RM) (n = 9) and of paired samples of histologically normal epithelium (HN) and ductal carcinoma in situ (DCIS) (n = 16). To determine how miRNA may control the expression of codysregulated mRNA, we also performed gene expression microarray analysis in the same paired HN and DCIS samples and integrated this with miRNA target prediction. We further validated several target pairs by modulating the expression levels of miRNA in MCF7 cells and measured the expression of target mRNA and proteins.
  
  
  RESULTS
  Thirty-five miRNA were aberrantly expressed between RM, HN and DCIS. Twenty-nine miRNA and 420 mRNA were aberrantly expressed between HN and DCIS. Combining these two data sets with miRNA target prediction, we identified two established target pairs (miR-195:CCND1 and miR-21:NFIB) and tested several novel miRNA:mRNA target pairs. Overexpression of the putative tumor suppressor miR-125b, which is underexpressed in DCIS, repressed the expression of MEMO1, which is required for ErbB2-driven cell motility (also a target of miR-125b), and NRIP1/RIP140, which modulates the transcriptional activity of the estrogen receptor. Knockdown of the putative oncogenic miRNA miR-182 and miR-183, both highly overexpressed in DCIS, increased the expression of chromobox homolog 7 (CBX7) (which regulates E-cadherin expression), DOK4, NMT2 and EGR1. Augmentation of CBX7 by knockdown of miR-182 expression, in turn, positively regulated the expression of E-cadherin, a key protein involved in maintaining normal epithelial cell morphology, which is commonly lost during neoplastic progression.
  
  
  CONCLUSIONS
  These data provide the first miRNA expression profile of normal breast epithelium and of preinvasive breast carcinoma. Further, we demonstrate that altered miRNA expression can modulate gene expression changes that characterize these early cancers. We conclude that miRNA dysregulation likely plays a substantial role in early breast cancer development.
authors.affiliation: Department of Medicine, Boston Medical Center and Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118, USA.
authors.forename: Bethany N
authors.initials: BN
authors.lastname: Hannafon
authors.forename: Paola
authors.initials: P
authors.lastname: Sebastiani
authors.forename: Antonio
authors.initials: A
authors.lastname: de las Morenas
authors.forename: Jining
authors.initials: J
authors.lastname: Lu
authors.forename: Carol L
authors.initials: CL
authors.lastname: Rosenberg
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015820:Cadherins / Q000096:biosynthesis; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D019159:Nonheme Iron Proteins / Q000096:biosynthesis; D063150:Polycomb Repressive Complex 1; D012333:RNA, Messenger / Q000096:biosynthesis; D012097:Repressor Proteins / Q000096:biosynthesis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C503627:CBX7 protein, human; D015820:Cadherins; C486625:DOK4 protein, human; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D047908:Intracellular Signaling Peptides and Proteins; C527585:MEMO1 protein, human; C531888:MIRN125 microRNA, human; C533449:MIRN183 microRNA, human; C552722:MIRN195 microRNA, human; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C538984:Mirn182 microRNA, human; D019159:Nonheme Iron Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D063150:Polycomb Repressive Complex 1